As disclosed in my U.S. Pat. No. 3,646,841, ultrasharp diamond edges are highly useful for molecular and submolecular sectioning at ultralow temperatures and as high intensity point sources for the emission of electrons, ions and neutrons. Such ultrasharp diamond edges --commonly referred to as "diamond knives"-- have also found other uses. For example diamond knives are used in surgery particularly in delicate operations such as operations on the eye. It has also been found that metals and other materials can be machined with a diamond knife in such manner as to obtain a perfectly smooth surface which is free of the scratches and other imperfections resulting from usual machining and polishing operations.
When used as point sources, diamond edges and points are coated with a thin film of a suitable material such as tungsten, rhenium, lanthanum, barium, caesium and other related materials of suitable work function and physical properties for electron emission. When thus coated, the diamond tip or edge serves as an effective emitter for electrons, ions, x-rays neutrons and other types of emission.
However, the use of ultrasharp diamond edges and points has been limited by the cost of production and by limitations on the size of diamond edges that could be made. As high quality diamond knives are made from diamonds of gem quality, the cost of such knives has accordingly been high. Moreover, by reason of larger diamonds not being available at an economically acceptable price, the length of the cutting edge of a diamond knife has been limited to less than ten millimeters and is usually in the one to three millimeter range. With respect to the use of diamond points and edges as cathodes or other emission electrodes, the useful life of the electrode has been limited by the dissipation of the metallic coating material. When such material has been depleted, it is necessary to discard or recoat the electrode. As such electrodes are normally hermetically sealed in an appropriate envelope, the removal, recoating, remounting and resealing of the electrodes may not be economically feasible.